Thermostatic control device



Oct. 21, 1952 J CAPARQNE 2,614,754

THERMOSTATIC CONTROL DEVICE Filed July 9, 1949 INVENTOR. (9108954 J.Cameo/m.

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Patented Oct. 21, 1952 THERMOSTATIC CONTROL DEVICE Michael J. Caparone,Arcadia, Calif., assignor to Robertshaw-Fulton Controls Company,Greensburg, Pa., a corporation of Delaware Application July 9, 1949,Serial No. 103,820

This invention relates to thermostatic control apparatus and, moreparticularly, to snap-action controls operated by thermally responsivehydraulic power elements.

\ Elements of the described type may have the filling fluid always undercompression and at an internal pressure greater than atmospheric. Insuch event, the control device which such elements operate does not moveto its safe position should the fluid begin to leak. It has beenproposed to counteract this unsafe feature by utilizing' a liquid filledpower element which, upon contraction of its liquid, exerts a pull forceon the control device to cause it to assume a fuel flow position. Shoulda leak develop in the system, then the liquid is not able to exert apull force to produce a fuel flow condition nor maintain such a positionif fuel is already flowing.

An object of the present invention is to. improve such so-calledfail-safe thermostats by insuringpositive operating characteristics incon-.

junction with the fail-safe feature.

.Another object of the invention is' to render the thermostatic controldevices operable under a variety of temperature ranges.

I Another object of the invention is to permit variations in the forceopposing the power element without affecting the normal operationthereof.

Another object of the invention is to facilitate changes in thetemperature rangeof the thermostat by minor changes in the powerelement.

Another object of the invention is'to reduce the size of the powerelement to a minimum.

Other objects and advantages will become apparent from the followingdescription taken in connection with the accompanying drawing wherein: IFig. 1 is a section through a portion of a thermostatic controlapparatus showingthe essential features of the invention, and "Fig. 2 isan enlarged view, partly in section, of the power element.

Referring more particularly to the drawing, the control apparatus isshown in Fig. l as comprising a casing I having an inlet opening I2 andan outlet opening M for fuel. The inlet l2 and outlet 14 communicatewith a valve chamber I5 provided in the casing and having an annularvalve seat It carried therein. A valve member 20 is positioned in thevalve chamber 16 for reciprocable movement relative to the valve seat 18between openand closed positions. The valve member Zilis normally biasedtoward the valve seat l8 and thus to its closed position by means 1Claim. (Cl. 236--48) action mechanism 26 for overcoming the bias of thespring 22 and causing movement of the valve z r i of a coil spring 22which is operative between the valve member 20 and a cover plate 24carried by the casing Ill and forming a closure for the valve chamber l6therein.

Snap action means, designated generally by numeral 26, are positionedcoaxial with and for operating the valve member 20 between its open andclosed positions. The snap-action means 26 cooperate for this purposewith a valve stem "28 which projects from the valve member 20 throughthe valve seat 18 for slidable movement in a guide support 3!] formed inthe casing'IO. The valve stem 23 is adapted for operative engage mentwith a clicker mechanism comprising a pair of opposed fulcrum levers 34,a fulcrum button 36 and a clicker disk 38, all of which are housedwithin a recess it! formed in the casing Iii beyond the guide support30. The clicker disk 38 is adapted to be operatively engaged by anannular thrust element 42 which is slidably mounted in. the recess inoverlying relationship with the clicker disk 38 and carries anupstanding collar 44 provided with a reduced stem portion 46 projectingexteriorly of the casing ID. As snap action devices of the type brieflydescribed herein are well known, further description is deemedunnecessary, except to point out that suitable provision is made, suchas by a gasket and gland 41', for sealing such mechanism against escapeof fuel from-the casing ll as .well known to those skilled in the art.In the absence of force applied to the thrust element 42, it is tobeunderstood that the valve member 20 is held in closed position underbias of the spring 22.

Means are provided for operating the snapmember 20 from closed to openposition. To this end, a thermally responsive hydraulic powerele-. mentis utilized in conjunction with lever means for transmitting movement ofthe power element through the snap action means 26 to the valve member20. The power element of this invention includes an expansible orbellows member 48, a capillary tube 50 and a bulb element 52 connectedin a closed system as is customary in such devices. The bellows member48, as more clearly shown in Fig. 2, is hermetically sealed to a plug.insert 54 suitably tapped for reception of one 3 between. The oppositeend of the-adjusting stem projects exteriorly of the casing I8 adjacentthe cover plate 24 and is also threaded for cooperation with manuallyoperable means in the form of a knob 62 which bears against the casingI8. Hence, rotation of the knob 62 causes the stem 56 to be reciprocatedin the casing l 8 on an axis substantially parallel with that of thesnap-action means 26. Consequently, the bellows member 48 moves towardor away from the casing [8 depending on the direction of rotation of theknob 62.

As is apparent from Fig. 2 of the drawing, the bellows member 48 has itsinner wall spaced from the plug insert 54 to provide. a space thereinfor a filling fluid 64. In this embodiment, the filling fluid 84 is anon-metallic liquid, such as xylene or aniline, or metallic, such asmercury, and is maintained under pressure always above that which wouldpermit vaporization throughout the range of temperatures that are to be.controlled by the thermostatic apparatus.

The; motion. transmitting means between the bellows member 48 and thesnap-action mechanism 26 takes the form of an angular lever member '68having one end overlying the bellows member 48 and being fastenedthereto by a stud T8. carried by the bellows member 48 and having a nut.12 for securing the lever 68in position thereon. The opposite end of thelever 68 is provided with a recess 14- for the reception of the end ofan adjusting screw 16 to provide a pivotal mounting. The adjusting screw16 is carried in a housing 18 for thelever 58 which also encloses thebellows member 48 and is secured by any suitable means (not shown). tothe casing Ill. The lever member 88 is fulcrumed intermediate its endson the upstanding collar 44 of the thrust element. 42 and for thispurpose. is provided with an aperture 88 through which the. stem 46extends. To secure substantially lineal. engagement of the lever member68 with the collar 44 on the thrust element 42, a depressed portion 82is formed on thev lever 68 adjacent the aperture 80 therein forproviding such engagement.

In the operation of the control apparatus described, the open osition ofthe valve member 28 as shown in Fig. 1 of the drawing, is the normalposition of this member whenever the temperature as sensed by the bulbelement 52 is below that for which the knob 62 has been set.v Thus,assuming that the snap-action mechanism 26 is normally in position toovercome the bias of the spring 22 on the valve member 20 and thetemperature afiecting the bulb element 52 increases, then the liquidfilling 64 expands and causes corresponding expansion of the bellowsmember 48. As the bellows member 48 is held bodily in its adjusted fixedposition by the adjusting stem 56, the .expansive movement results in amovement of the stud 18 away from the casing l causing acounterclockwise pivoting movement of the lever member 68 about theadjusting screw 16. The collar 44 on the thrust element 42 follows thecounterclockwise movement of the lever 88 and causes the clicker disk 38of the snap-action mechanism to move to its retracted position. The biasof the .valve spring 22 is then exerted to cause closure of the valvemember 28 relative to the valve seat l8. Consequently, flow of fuelbetween the inlet l2 and the outlet l4 ceases.

In the event that the temperature sensed by the bulb element 52decreases, then the liquid 84. will contractand the bellows member 48will exert a pull on the lever member 68 causing it to rotate clockwiseon its pivot I6 toward the casing I0. Such motion of the lever 68 willbe transmitted to the thrust element 42 of the snap-action mechanism 26which overcomes the bias of the valve spring 22 and causes the valvemember 20 to be moved to its open position as shown in Fig. 1 of thedrawing. As so. far described, the opening and closing movements of thevalve member 20 due to operation of the snap-action mechanism followsthat of any thermostatic control apparatus constructed as described andregardless of the internal pressure used. in the power element. However,should the power element of this invention become punctured. orotherwise develop a leak, then the tension. of the liquid 64 is relievedand the internal pressure will increase to the atmospheric pressure.existing externally of the power element. Consequently, the return snapforce of the clicker disk 38 will be exerted to mechanically expand thebellows. 48 and. cause operation. of the. lever 88 in a counterclockwisedirection. .As. previously explained, the bias of the valve spring 22can then be exerted to cause closure of. the valve member 28 relative toitsseat I8. It is apparent, therefore, that the control element of this.invention always fails in a safe condition, due to immediate closure ofthe valve member 20 when such failure occurs.

It will further be apparent that the bellows member 48 is normallymaintained in tension, but is adapted to expand solely by volumetric.changes in the liquid 64 upon sufficient variation in the temperaturecondition sensed ,by the bulb element 52. The volume of liquid 64contained in the power element does not change appreciably for verylarge changes of. pressure. Liquids. offer. great resistance to changesof their volume while gases or vapors ofier very little resistance. Thecoefficients of compressibility of the non-metallic liquids, xylene andaniline, are about .000074 and, .000043, respectively. Hence, negligiblechange in linear expansion of the bellows member 48 is experienced. Theapparatus, therefore, exhibits great advantages over those utilizingpower elements with liquid under compression or involving vapor pressurechanges. In the disclosed-embodiment, a normally closed snap mechanismis combined with the fail-safe power element to reduce the internalfluid pressure of the latter and obtain the desired safe failure.

Many changes may be made in the details of construction and arrangementof parts within the scope of the appended claim as will be apparent.

I claim:

A thermostatic control apparatus comprisinga casing having inlet andoutlet openings for fuel, a valve seat intermediate said openings, avalve member reciprocable relative to said seat between open and closedpositions and being biased to said closed position, a valve stem carriedby said valve member and projecting toward said seat, snap-action meansmounted in said casing coaxial with said valve member on the oppositeside of said seat, said means including spring means adapted foroperative engagement with said valve stem for overcomin said bias andcausing movement of said valve member to said open position, anexpansible bellows member positioned in said casing for movement on anaxis substantially parallel with said valve member, a lever pivoted atone end in said casing and overlying said snap-action means and. saidmitting a biasing force from said spring means to said bellows memberfor urging said bellows member toward elongated condition, a bulbadapted to be exposed to variation in a temperature condition, acapillary tube connecting said bellows member and bulb in a closedsystem, liquid under pressure less than atmospheric completely fillingsaid system for nomially maintaining said bellows member in tension butbeing adapted for causing expansion thereof solely by volumetric changesin said liquid upon sufiicient variation in said temperature condition,an adjusting stem carried by said casing for supporting said bellowsmember for bodily movement relative to said snap-action means, andmanually operable means projecting exteriorly of said case ing foractuating said adjusting stem to overcome said bias and hold said valvemember in i open position in the absence of said or leakage in saidsystem. r

i MICHAEL J. CAPARONE.

expansion REFERENCES CITED The following references are of record in thefile of this patent:

UNITED STATES PATENTS

